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74 R90/6 Ignition question(s)

Afternoon everyone. I've recently picked up an old R90/6, which runs great once it's started. The thing seems to drag down the battery considerably using the electronic ignition. I've been chasing various threads across the internets, just doing regular old research and have learned quite a lot about how the ignitions/charging systems work on these old things. Hell, that's why I picked the thing up, i really want to learn the stuff.

So, after a weekend of basically just doing research, i'm thinking that, because my riding is city-riding, that i'm just not getting the rpms up high enough to really recharge the battery, which is kind of leading me down the path of possibly grabbing one of those Omega 450 systems, which would hopefully go a long ways towards my charging woes.

The second issue seems that the electronic ignition (brand is Martek) just really seems to lug the engine turnover and i'm thinking, after googling the brand, that it just may be kind of a piece of junk.

A little history on the bike - it was a daily rider for a friend until about three years ago, and has sat in the garage since. After a new battery, new gas, new oil etc, it fired up on the first push of the button, though it didnt whip the engine around, just kind of rolled it a couple times and the bike started.

I'm still just looking around for possible solutions, but the bike is almost 40 and replacing those two things seem like they may do the trick.

Anyone have any thoughts...

Also, one other really dumb question - if a bike has an electronic ignition - does it not use the points anymore? I hear of people going back and forth between the two and i dont quite follow.

I would consider an adjustable regulator first to bump up the voltage to the battery for charging. Much cheaper than an new charging system!! If that doesn't work, then consider the a change in the charging system. Or consider a battery tender to keep the battery charged...also cheaper!

I'm trying to understand how an electronic ignition system lugs or pulls down the starter?? The ignition system is virtually touch-free. Could it be that the starter needs some work instead? You said you're not charging the battery...is the battery not fully charged up?

I'd be interested to hear others...I think you're make some assumptions that aren't really correct.

About 10 years ago I bought a R90S that had been totally restored by two friends of mine. The bike had a Boyer ignition, at least I think it was a Boyer. The ignition curve was built into the unit because the mechanical advance unit, along with the points, were removed and replaced with a PCB that had a coil/magnetic pickup.

When it tried to turn over it sounded like it was too far advanced, like it was kicking back, thus loading down the starter. I checked the timing and it seemed ok at full advance, but too advanced at idle. If I retarded it a to correct it at idle it started ok, but it would never reach the timing mark at full advance.

I took it off and installed the stock points and advance unit. It started just fine and ran fine, and I could get it timed correct at the static mark and the full advance. I sold the bike to a friend and helped him install a Dyna III ignition on it, like I had on my 78 Motorsport. The pinging he was experiencing went away, and it started even better.

I bet your bike is advanced too much and the starter is being kicked back by the bike firing too early. Hope this helps.

I would consider an adjustable regulator first to bump up the voltage to the battery for charging. Much cheaper than an new charging system!! If that doesn't work, then consider the a change in the charging system. Or consider a battery tender to keep the battery charged...also cheaper!

I'm trying to understand how an electronic ignition system lugs or pulls down the starter?? The ignition system is virtually touch-free. Could it be that the starter needs some work instead? You said you're not charging the battery...is the battery not fully charged up?

I'd be interested to hear others...I think you're make some assumptions that aren't really correct.

i'd initially thought about a new voltage regulator, and still may go that route because they're really *cheap* compared to the full charging system.

i suspect i'm just describing the starting situation poorly - hit the button and it lugs a couple times before starting up. if the battery isnt fully charged, it lugs like 4x and doesnt start.

at the moment, i've got the battery on a tender to get it back up to charge (after jacking with it this weekend). it's a new battery, but that tender is slowsville for getting it back to top-charge. i've got a better charger on the way, so at the moment, i'm just kind of cleaning the rims

I think you're describing the lugging starter right, but I still think it's not associated with the EI. Now if the Martek is robbing THAT much power, then it could be. The only way to know is to convert back to points without making any other changes and see if the situation improves.

It would be my suggestion to approach this systematically.

1) A battery tender will not charge a completely dead or significantly depleted battery. They're for just for topping off.
2) What is the voltage at the battery when the engine is running above 3K RPM? You'll need a separate good voltmeter to measure that.
3) You could be getting good voltage to the battery, but not enough current. This would be due to dirty or corroded connections and/or battery cables that look fine but have significant corrosion built up so that the current flow is restricted.
4) Add a grounding harness to the diode board. This will improve the output of the diode board.
5) The 3-wire cable from the output of the alternator to the diode board can corrode behind the diode board depending on the type of cable. Replace that cable.
6) Adding solid mounts for the diode board to the engine case can improve heat transfer and grounding. See 4) above.
7) Your brushes might not be making good contact to the rotor...if they are shortish, the springs won't keep them solidly in touch with the rotor.

Is your charge light acting properly? It should come on with key on engine not started. Then at 1500 RPM or so, it should go out, and never come back on again, except occasionally at idle.

Look into all these things before you start throwing serious money at it. This would be in keeping with the continued learning process.

Kurt, my bike had the same symptoms. It turned over very slowly, straining, then would start on the second or third revolution. It felt like the starter was struggling, which it was. It almost made a "chug, chug" sound. Just retarding the timing with the Boyer fixed that, it would turn over at normal speed while cranking, but it had the advance problem then. The bike had a new battery and the bike has been fine for the past 10 years. Checking battery voltage is a good idea, the first thing to do actually, but before I would replace anything I would check the timing.

I see what you're saying...fighting the compression maybe more than it should. I would have thought that a healthy starter system should be able to keep up with slight changes in the timing. Certainly, no cost in checking that!! Then move on to "low hanging fruit" before buying the fruit stand!!!

Low hanging fruit would be to clean the ground cable and where it connects to the block. Is the new battery you bought appropriately sized? There are some bits on the starter you can clean/lube as well.

Kurt mentioned an adjustable voltage regulator, and you mentioned a two week old battery .... but have you measured the actual voltage that is being delivered to the battery right now?? You will want the battery "topped off" when you check the charging system.

Last edited by lmo1131; 07-28-2013 at 09:23 PM.

"It is what you discover, after you know it all, that counts." _ John Wooden

There are lots of contributing factors to the problems you describe. Poor connections, bad grounds, corrosion inside the three wire bundle that goes from the alternator to the diode board, worn out brushes, a marginal diode board, starter in need of a rebuild, bike not tuned correctly, older style mechanical voltage regulator.

Just putting in the high output charger won't overcome all that.

So maybe, the way to go is to work your way through the other stuff, and when you know you have it right, if you still feel that using a Tender to keep the battery topped is not working, then spend the money on the high output charging system.

One last thought - lots of debate about electronic ignitions versus points. No clear cut winner. However, most of the electronic ignitions are Dyna 3 if your advance unit is still ok, or Boyer, if you have a problem with the advance, or stripped the tip of the cam where the advance unit attaches. Not much discussion about Martek, so that is an unusual type of electronic ignition.

You wanted to learn about the early machines so you bought a bike with an electronic ignition conversion?

Find the parts to rebuild, replace the OEM ignition points. After one year of this you can put a Booster on it but keep the points and keep the mechanical advance.

Rebuild or replace the starter. Charge the battery or replace the battery and learn to ride in the city while keeping the rpms up. I never shift below 4,000 rpm in the city. I never coast at less than 3,000 rpm. The charging circuit will work at these revs.

Not to hijack this thread, but I drop my feet and drag the right one through some gravel usually found on the side of the road. Works wonders, most of the time they back off immediately. A friend was riding the R90S that I sold him and was rear ended, not a pretty site.